The present invention relates to fans such as ceiling fans and room fans for air circulation and/or ventilation within building structures and the like.
Ceiling fans for air circulation are well known, typically having four to six blade paddles that extend outwardly from a motor that is suspended below the ceiling of a room. The blade paddles are planar and extend to an outside diameter that is usually between four and five feet from proximate a centrally located motor that is relatively large, being typically 9 to 14 inches in diameter. As shown in FIGS. 1 and 2, conventional ceiling fans produce a generally torroidal flow pattern in which vertical flow goes in one direction near the center of the room, and in an opposite direction near the walls. Other ventilation fans of the prior art include units having a grille or bezel that clamps to a wall or ceiling surface about a duct opening. One such unit having an annular array of openings surrounding a lamp is shown in U.S. Design Pat. No. 340,514 to Liao. Other types of room fans are also well known, including table fans and floor fans for producing predominately horizontal circulation.
The fans of the prior art are not entirely satisfactory in that they exhibit one or more of the following disadvantages:
1. They are ineffective in providing a desired amount and distribution of circulation; PA1 2. They are inefficient in that they exhibit excessive aerodynamic drag for a given amount of circulation due to the combination of a wide variation in blade speed from the tip toward the motor, and the motor or other bulky central structure blocking axial flow; PA1 3. They are dangerous in that accidental contact with moving parts is likely to produce serious injury; and PA1 4. They are excessively noisy.
Thus there is a need for a fan that overcomes the disadvantages of the prior art.